Re: [Xen-devel] kasan_map_early_shadow() on Xen

From: Juergen Gross
Date: Tue Mar 03 2015 - 23:53:16 EST

On 03/03/2015 08:20 PM, Luis R. Rodriguez wrote:
On Tue, Mar 3, 2015 at 2:06 AM, David Vrabel <david.vrabel@xxxxxxxxxx> wrote:
On 03/03/15 09:40, Luis R. Rodriguez wrote:

I believe that on Xen we should disable kasan, would like confirmation

Why? This is the first of heard of this.

Andrey chimed in here confirming this.

from someone on xen-devel though. Here's the thing though -- if true
-- I'd like to do it *properly*, where *properly* means addressing a
bit of architecture. A simple Kconfig slap seems rather reactive. I'd
like to address a way to properly ensure we don't run into this and
other similar issues in the future. The CR4 shadow issue was another
recent example issue, also introduced via v4.0 [0]. We can't keep
doing this reactively.

Let's go down the rabbit hole for a bit. HAVE_ARCH_KASAN will be
selected on x86 when:


Now Xen should not have SPARSEMEM_VMEMMAP but PVOPs' goal is to enable

Why? Again, this is the first I've heard of this as well. FWIW, all
the Xen configs we use have SPARSEMEM_VMEMMAP enabled.

Interesting... we have config ARCH_SPARSEMEM_ENABLE depend on !XEN at
SUSE. Figured this was a generic issue. The SUSE kernels are based on
3.12 though, but anyway with it enabled I do get compile failures
because of redefinition of MAX_PHYSMEM_BITS which we provide on Xen
set to 43 for some reason (can't find that justification), so it
doesn't use the default 46 that would be used otherwise. But another
reason seems to be the lack of forward porting yet PAT support for PV
domains -- commit 47591df50 upstream which requires us to still have
the union on the pte_t, and I suppose we need ca15f20f as well...

If there is nothing else I suppose this just requires fixing up at

The SUSE kernel has several patches renaming/altering Xen-related config
options. Don't mix that up with upstream/pvops.

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at